基于容抗法的C_(DM)测试技术设计

Design of C_(DM)Test Technique Based on Capacitance Method

网络运放输入差模电容可通过电容不同特性计算推导,而实际测试设备的精度往往无法达到理论推导结果的准确性,这主要是由于运放差分输入OFFSET问题导致差分输入信号无法达到完全一致。首先,为了深入地了解寄生电容的主要产生机制,对传统Bipolar器件和CMOS器件的结构以及等效模型进行了分析介绍;然后,分别根据运放频域特性和寄生电容的充放电特性原理,对运放的输入差分寄生电容进行推导;最后,利用仿真方法对测试结果进行了验证。结果表明,采用容抗法测得的结果更接近于真实值,从而验证了所提出的方法的有效性,对于提高差模电容测试精度具有重要的意义。

The input differential mode capacitors of network operational amplifier can be calculated and deduced through different characteristics of capacitors.However,the accuracy of actual test equipment is often unable to reach the accuracy of the theoretical deduction results,which is mainly because the differential input signals cannot reach complete consistency due to the OFFSET problem of operational amplifier differential input.Firstly,in order to deeply understand the main generation mechanism of parastic capacitance,the structure of traditional Bipolar devices and CMOS devices and equivalent model are analyzed.Then,according to the frequency domain characteristics of the operational amplifer and the charge-discharge characteristics of the parasitic capacitor,the input differential parasitic capacitance of the operational amplifier is derived.Finally,the simulation method is used to verify the test results.The results show that the measured results by the capacitance method are closer to the real values,which verifies the effectiveness of the proposed method and has important significance for improving the measurement accuracy of differential mode capacitance.